The present invention relates to a disc brake caliper arrangement and, more particularly, a seal arrangement surrounding a piston provided within the disc brake caliper which provides both sealing and rollback function.
Disc brakes and disc brake calipers are known and have been widely used in the art. Typically, these devices include a caliper housing which surrounds the disc brake rotor and which housing includes a pair of brake pads on opposite sides of the disc rotor. A piston is slidably mounted in an inwardly directed portion of the brake housing. The piston is hydraulically actuated through a brake line connected to the caliper housing. Upon actuation, the piston is translated and the inner brake pad which then frictionally engages the brake pad with the rotor and simultaneously pulls the other end of the housing toward the outer brake pad into frictional engagement with the brake rotor disc mounted to the wheel of the vehicle. These devices have utilized a seal disposed in a groove in the housing of the caliper which seal engages the outside diameter of the piston. The seal performs an important function in that after actuation of the disc brake, and the resulting deformation of the seal toward the inner brake pad, return of the piston is accomplished by the so-called rollback of the seal wherein the seal returns the piston to its initial position thereby providing a running clearance for the brake system. This running clearance is required to avoid roughness of the brake operation if the clearance is too little and conversely spongy operation of the brake system if the clearance is too great. In these known systems, the seal is provided in a groove of the caliper housing which is further provided with a substantial chamfer along the inner edge of the caliper housing. This chamfer provides an area for the seal to deflect upon actuation of the brakes and relaxation of the seal once the braking operation is completed. Relaxation of the seal is intended to retract the piston to its normal position thereby providing the required running clearance as discussed above. It has been found that the required retraction for running clearance provided by these prior art disc brake caliper seals is unsatisfactory with respect to both brake roughness and spongy brake pedal movement.
These and other disadvantages are overcome by the present invention wherein a disc brake caliper seal arrangement is provided wherein a novel seal arrangement is provided which eliminates the need for providing a machine chamfer in the caliper housing and wherein the resulting running clearance is optimized and variation about this point minimized.